Some studies have suggested that phallometrically derived rape indices
can differentiate groups of rapists and non-offenders. There are othe
r studies however which cast doubt on this assertion, at least in so f
ar as it applies to all but those few rapists who are sadistic. These
studies have used rape indices which are derived from rapists' sexual
responses to audiotaped descriptions of mutually consenting sex and br
utal sexual assaults. It was hypothesized however, that stimuli which
put more emphasis on the degrading and humiliating elements of rape wo
uld improve discriminability. Stimuli were compiled to test this hypot
hesis. The results indicate that neither rape indices derived from the
physically brutal elements nor the degrading elements of rape were ab
le to discriminate between rapists and non-offenders. Furthermore, the
se indices were not related to offence histories. The results are disc
ussed in terms of their implications for the assessment of rapists and
theoretical considerations of their behaviour.